Indications: Saw palmetto is used by natural health practitioners to treat a variety of ailments in men and women, such as testicular inflammation, urinary tract inflammation, coughs, and respiratory congestion. It is also used to strengthen the thyroid gland, balance the metabolism, stimulate appetite, and aid digestion

Preparations: tablets, capsules, and a liquid extract

Therapeutic classification index:
Genito- urinary system: It relaxes the bladder and urethra
Respiratory system: It affects the respiratory mucosa and is used in chronic catarrh.
Reproductive system: It increases the nutrition of testicles.

Pharmacology
The mechanism by which saw palmetto may be useful to treat the symptoms of benign prostate hyperplasia is not completely understood. In vitro pharmacodynamics studies indicate that S. repens may have multiple mechanisms of action in BPH. The mechanisms most likely involved include inhibition of type 1 and type 2 isoforms of 5a
-reductase, inhibition of binding of dihydrotestosterone to cytosolic androgen receptors in prostate cells, and alpha1-adrenergic blocking activity. Mechanisms also possibly involved but less well demonstrated are inhibition of prolactin and growth factor–induced prostatic cell proliferation, an antiestrogenic activity, and/or an anti-inflammatory effect.

Inhibition of 5a
-reductase activity In vitro
Saw palmetto may act by inhibiting 5 a
-reductase, the enzyme responsible for conversion of testosterone to dihydrotestosterone (DHT). Several in vitro experiments in cultured human foreskin fibroblasts have found extracts of Serenoa repens to be strong and specific inhibitors of the enzyme 5a
-reductase. Studies using an eukaryotic (baculovirus-directed insect cell) expression system found that LESP (liposterolic extract) inhibits activity of both isoenzymes of 5-reductase, whereas finasteride selectively inhibits type 2. Moreover, finasteride demonstrates a competitive inhibition, while LESP displays noncompetitive inhibition of the type 1 isozyme. Similarly, an experiment performed on rat prostate gland cells using an n-hexane extract of Serenoa repens at an IC50= 88.2 ± 2.6 µg/mL showed specific inhibition of the enzyme 5-reductase, which thereby slowed the conversion of testosterone to DHT 17.

In vivo human/animal
A 7-day study in which testosterone-stimulated, castrated rats were given an n-hexane extract of Serenoa repens at doses of 180 or 1800 mg per day found no 5a
-reductase inhibition nor decrease in serum DHT. A similar 7-day study in healthy male volunteers given 160 mg twice daily found similar results an explanation for the conflicting observations from previous studies, the authors suggest that the high doses used in the prior studies resulted in the non-specific inhibition of 5 a
-reductase and androgen binding. They contend that the doses used by the earlier investigators were supraphysiologic and thus not clinically relevant.

Alpha1 adrenergic blocking activity In vitro
Several phytotherapeutic agents, including saw palmetto extract oils, were tested for their ability to inhibit [a3H] tamsulosin binding to human prostatic a1-adrenoceptors and [a3H] prazosin binding to cloned human a1A-and a1B-adrenoceptors in rat-1 cells. All saw palmetto extracts inhibited radiolig and binding to human alpha1-adrenoceptors in a non-competitive, concentration-dependent manner. Extract oils and powders were tested. For the two extract powders, maximum inhibition was obtained with 125 and 160 µg/mL and was 74 ± 4% and 59 ± 17%, respectively. The saw palmetto oils behaved slightly differently. They inhibited [a3H] prazosin binding almost completely.

Antiandrogenic and antiestrogenic activity In vitro
The antiandrogen effects of saw palmetto have been reported in several in vitro experiments demonstrating its inhibitory effect on the binding of DHT to androgen receptors in the cytosolic component of prostate cells. One in vitro experiment using isolated rat prostate found that a saw palmetto n-hexane extract at concentrations of 0.33 mg/mL inhibited the binding of a synthetic androgen to cytosolic receptor sites. Results of another in vitro experiment demonstrated that a liposterolic extract of Serenoa repens inhibited binding of dihydrotestosterone to androgen receptor sites in cultured human foreskin fibroblast. Experiments using human tissue samples (i.e., abdominal wall skin, myometrium, prepuce, and vaginal skin) found that n-hexane extract of Serenoa repens inhibited dihydrotestosterone and testosterone binding by approximately 40%. The authors of an experiment to study the effects of a liposterolic extract of saw palmetto (LESP) on two prostatic cancer cell lines differing in androgen responsiveness also concluded that their findings supported anti-androgenic activity of the extract. Variable concentrations ( 10 mg/mL to  25 mg/mL) of an n-hexanepreparation antagonized androgen-stimulated cell growth in a concentration-dependent manner. Binding of DHT receptors is not an unequivocal finding, however. One study further tested the effect of saw palmetto on DHT binding using a liposterolic extract produced by supercritical CO2 extraction. No effect on the (3H) dihydrotestosterone binding either with an undiluted extract or with dilutions up to 1:1000 was observed.

In vivo animal
A study using hormone-treated castrated rats found that administration of an n-hexane extract of saw palmetto for 90 days inhibited hormone-induced total prostate weight, with maximum benefits beginning 30 days after treatment was begun. A similar study used xenografts of human benign hyperplastic prostate tissue transplanted into three groups of athymic nude mice. In groups II and III the tissue was stimulated with the hormones 5a
-dihydrotestosterone and estradiol. Group I received no treatment and served as the control. In addition, animals of group III were treated with the lipophilic extract of saw palmetto. Significant inhibition of tissue growth was observed in group III as compared with group II (P 0.05). However, histologically no differences were visible between groups II and III. In group I (the control) atrophy of the graft was observed as expected.

Other hormonal effects In vitro
Several researchers have investigated the inhibition of prostate growth by blocking the binding of prolactin to specific receptors in the prostate and/or interfering with signal transduction processes. Pretreatment of Chinese hamster ovary cells with 1 to 10 mg/L of LESP completely inhibited the effects of prolactin on various pathways of receptor signal transduction and ultimately prolactin-induced prostatic growth. Human prostate tissue samples biopsied from patients with BPH were cultured in vitro with the presence or absence of basic fibroblast growth factor (b-FGF) or epidermal growth factor (EGF). The saw palmetto extract did not significantly inhibit basal cell proliferation at any dose when separately compared with b-FGF. However, when saw palmetto was incubated with either b-FGF or EGF, it significantly inhibited both b-FGF and EGF-induced cell proliferation at the highest dose of 30 g/mL.

In vivo human
In an effort to demonstrate that LESP has a multi-site mechanism of action, twenty-five men with BPH were randomly assigned to two treatment groups, a control group receiving no treatment and a treatment group receiving 320 mg per day of an n-hexane extract for 3 months. Each patient then underwent suprapubic biopsies from three prostatic regions: periurethral, subcapsular, and intermediate. The concentration of testosterone (T), dihydrotestosterone (DHT), and epidermal growth factor (EGF) in each prostatic region was measured by radioimmunoassay. Each prostatic region was evaluated with radioimmunoassay for levels of testosterone (T), dihydrotestosterone (DHT), and epidermal growth factor (EGF). Those treated with saw palmetto exhibited regionally distinct, statistically significant reductions in prostatic DHT and EGF levels along with an increase in T levels. Lower DHT (2363 ± 553 pg/gram, (P < 0.001) and EGF (6.98 ± 2.48  g/gram tissue, P < 0.001) values in the periurethral zone and an increase in T values in all three prostatic regions, with the highest values seen in the periurethral area (1023 ± 101 pg/gram tissue, P < 0.001) demonstrate the capacity of the extract to inhibit in vivo 5-reductase in human pathological prostate. These biochemical effects, particularly in the periurethral region, may be associated with the clinical improvement of the obstructive symptoms of BPH.

Another study in BPH patients receiving 160 mg of a saw palmetto extract twice a day for 30 days reported no change in plasma concentrations of testosterone, follicle-stimulating hormone, or luteinizing hormone. The authors concluded that saw palmetto does not act via systemic changes of hormone levels.

Anti-inflammatory activity In vitro
Several studies demonstrated that inhibition of synthesis of inflammatory metabolites of arachidonic acid, through a double blocking of cycloxygenase and lipoxygenase pathways, could be involved in the anti-inflammatory and antiedematous properties shown by the S. repens extract. An in vitro study of LESP prepared by supercritical fluid extraction with carbon dioxide, separated into three fractions, found the fraction containing the acidic lipophilic compounds to be a dual inhibitor of cyclo-oxygenase and 5-lipoxygenase in the acidic lipophilic fraction, while the fatty alcohols and sterols were inactive. Another in vitro study demonstrated the potent inhibition of the production of 5-lipoxygenase metabolites (especially leukotriene B4) by LESP (Permixon®) The production of 5-lipoxygenase metabolites was inhibited at concentrations as low as 5 µg/mL and 50% inhibition was achieved with concentrations of approximately 13 µg/mL 3.

Antispasmodic activity In vitro
The spasmolytic effects of two lipophilic extracts from saw palmetto (total lipidic and saponifiable) were studied on isolated smooth muscle of rat uterus, bladder, and aorta. The antispasmodic activity appeared to be related to inhibition of calcium influx and an activation of the sodium/calcium ion exchanger. Follow-up research suggested that cyclic AMP might be a possible mediator, together with the involvement of post-transcriptional induction of protein synthesis.

Role of Sabal n prostate enlargement

1) Six-month-long carefully controlled study by physicians at the University of Chicago, published in the December issue of the journal Urology, shows that the herbal remedy saw palmetto can improve symptoms for men with lower urinary tract problems, but that it has no significant impact on urinary flow rates, quality of life, or sexual function

2) Saw palmetto has been widely accepted to be beneficial to deter the progression of prostate enlargement due to its inhibitory capability of 5-alpha-reductase activity, and as a corollary, Saw palmetto may also prevent hair loss. A review article authored by T.J. Wilt, C. Mulrow and their colleagues (JAMA 1998 Nov 11;280(18):1604-9) is cited.

Saw palmetto berry extract inhibits cell growth and Cox-2 expression in prostates cancer cells.
The cytotoxicity of a commonly used material to alleviate the symptoms of benign prostatic hyperplasia (BPH), Saw Palmetto Berry Extract (SPBE), was examined as neat oil using a set of prostatic cell lines; 267B-1, BRFF-41T and LNCaP. Proliferation of these prostatic derived cell lines is inhibited to different degrees when dosed for 3 days with SPBE. The amount of SPBE required to inhibit 50% growth (IC50) of these cell lines was 20-30 nl equivalents of SPBE per ml of medium for cell lines 267B-1 and BRFF-41T and approximately 10-fold more for the LNCaP cell line. The effect of [Saw palmetto berry extract] dosing on these cell lines is not irreversible, since a 30 min treatment with SPBE at an IC50 concentration does not inhibit their growth. Normal prostate cells were inhibited by 20-25% when grown in the presence of 200 nl [Saw palmetto berry extract] equivalent per ml media. Growth of other non-prostatic cancer cell lines, i.e. Jurkat and HT-29, was affected by approx. 50% and 40%, respectively. When LNCaP cells were grown in the presence of dihydrotestosterone and [Saw palmetto berry extract], the IC50 concentration decreased significantly compared to LNCaP cells grown in the presence of serum and [Saw palmetto berry extract]. Reduced cellular growth after [Saw palmetto berry extract] treatment of these cell lines may relate to decreased expression of Cox-2 and may be due to changes observed in the expression of Bcl-2. Expression of Cox-1 under similar conditions is not affected because of its constitutive expression. Since increased Cox-2 expression is associated with an increased incidence of prostate cancer, and decrease in its expression by [Saw palmetto berry extract] would provide a basis for further investigation of its use against BPH and in prostatic cancer chemoprevention.

Uses in women
There is very little documentation or scientific research into saw palmetto use in women. However, several studies in the 1990s show that the BPH drug can be effective in stopping unwanted facial and body hair growth, and in treating thinning hair in women. It works by blocking the action of an enzyme called 5-alpha reductase. Anecdotal reports suggest that saw palmetto effective in treating unwanted hair growth and thinning hair, and in preventing some types of acne. It has also been used to treat urinary tract inflammation and help relieve the symptoms of menstruation. There are claims it can be used to enlarge breasts, but these claims have not been scientifically tested